EP0706157A1 - Système électronique impulsionnel de surveillance d'article - Google Patents

Système électronique impulsionnel de surveillance d'article Download PDF

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Publication number
EP0706157A1
EP0706157A1 EP95111028A EP95111028A EP0706157A1 EP 0706157 A1 EP0706157 A1 EP 0706157A1 EP 95111028 A EP95111028 A EP 95111028A EP 95111028 A EP95111028 A EP 95111028A EP 0706157 A1 EP0706157 A1 EP 0706157A1
Authority
EP
European Patent Office
Prior art keywords
suppressing
transmitting
antenna
transmitting antenna
output terminals
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95111028A
Other languages
German (de)
English (en)
Other versions
EP0706157B1 (fr
Inventor
Brent Balch
Dave Roberson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sensormatic Electronics Corp
Original Assignee
Sensormatic Electronics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sensormatic Electronics Corp filed Critical Sensormatic Electronics Corp
Publication of EP0706157A1 publication Critical patent/EP0706157A1/fr
Application granted granted Critical
Publication of EP0706157B1 publication Critical patent/EP0706157B1/fr
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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2477—Antenna or antenna activator circuit

Definitions

  • This invention relates generally to electronic article surveillance (EAS) and pertains more particularly to improved EAS systems.
  • One present commercially implemented EAS system has a transmitter which radiates a pulsed magnetic field into a surveillance area wherein it is desired to note the presence of articles bearing EAS tags.
  • a tagged article When a tagged article is present in the surveillance area, its tag is excited by the radiated magnetic field and, based on its composition, is caused to generate a detectable response signal.
  • a receiver which is enabled between successively spaced transmitter field radiations, detects the response signal of the tag and initiates an alarm or other activity to indicate the presence of the tag in the surveillance area.
  • transceiver antennas wherein the transmitter and receiver coils are in very close proximity.
  • current flowing in the transmitting antenna coil induces a secondary current in the closely coupled receiver antenna coil.
  • the receiver antenna coils typically has many more turns than the transmitter coil, so there is a step-up transformer at hand.
  • To produce peak transmitter currents of ten amps requires several hundred volts to be developed across the transmitter coil.
  • the transformer relationship between antennas means potentials of two thousand volts or more could be induced across the receiver antenna coils. This could lead to voltage breakdown between the windings of the receiver coil, as well as damage to the sensitive receiver circuit input.
  • a common technique for protecting both the receiver coil itself and the receiver circuitry is to connect two semiconductor diodes in an anti-parallel arrangement across the receiver coil, i.e., the diodes are oppositely polarized.
  • the diodes are oppositely polarized.
  • the diode conducts, limiting the maximum terminal voltage across the receiver to approximately two volts peak-to-peak.
  • the transmitting coil is of course subject to the receiver coil radiated magnetic field.
  • the transmitter radiated field thus undesirably contains such diode-caused harmonic distortion and system transmissions are of lesser quality than is desired.
  • the present invention has as its primary object the improvement of existing EAS systems.
  • a quite general object of the invention is to improve the quality of transmissions in EAS systems.
  • a more particular object of the invention is to overcome the above-noted disadvantage in transmitter radiated fields based on need for receiver protection.
  • an EAS system including a transmitting antenna, drive means operable for exciting the transmitting antenna, a receiving antenna and means connected to the receiving antenna for improving the quality of transmissions. It is submitted as unique in EAS systems to look to the receiver for improving transmission quality. Thus, the art has heretofore addressed the receiver and its antenna only in respect of processing tag signals.
  • the drive means excites the transmitting antenna at a preselected system operating frequency and the means connected to the receiving antenna improves the quality of transmissions by lessening harmonics of the operating frequency in the transmissions.
  • the invention provides in combination, in an EAS system having successive transmitting and receiving periods and having a preselected operating frequency: a receiving antenna having output terminals; and suppressing means connected to the receiver terminals and operable during the transmitting periods for suppressing the presence therein of signals which are harmonics of the preselected operating frequency.
  • the invention provides, in a more particular combination, a transmitting antenna, drive means operable for exciting the transmitting antenna at a preselected frequency, a receiving antenna in electromagnetically coupled relation with the transmitting antenna and having output terminals, suppressing means connected to the receiver terminals and operable for suppressing the presence of signals therein which are harmonics of the preselected frequency and control means for concurrently rendering the drive means and the suppressing means operable.
  • the invention provides a transmitting antenna, drive means operable for exciting the transmitting antenna at a preselected frequency, a receiving antenna in electromagnetically coupled relation with the transmitting antenna and having output terminals, means connected to the output terminals for limiting voltage thereacross, and suppressing means connected to the receiver terminals and operable for suppressing the presence of signals therein which are harmonics of the preselected frequency.
  • the system further includes control means for concurrently rendering the drive means and the suppressing means operable.
  • the suppressing means comprises circuitry having a linear conduction characteristic and may be constituted by an electronic switching circuit.
  • the electronic switch comprises first and second pairs of field effect transistors connected in parallel across the receiver coil output terminals.
  • the electronic switch comprises first and second field effect transistors connected in parallel across the receiver coil output terminals.
  • Fig. 1 is a block diagram of an EAS system in accordance with the invention.
  • Fig. 2 is an electrical schematic diagram of a preferred version of harmonic suppressor 32 of the Fig. 1 system.
  • Fig. 3 is an electrical schematic diagram of a further version of a harmonic suppressor.
  • the EAS system arrangement therein includes a transceiver antenna having an outer coil 10, constituting the transmitting antenna, and an inner coil 12, constituting the receiving antenna.
  • the transmitting antenna is energized by TX ANTENNA DRIVER 14 over lines 16.
  • the receiving antenna output terminals are connected to lines 18 and 20 and output signals are conducted over lines 22 and 24 to RX ELECTRONICS 26 for processing thereof to detect tags.
  • lines 18 and 20 are further connected by lines 28 and 30 to TX TIME HARMONIC SUPPRESSOR 32, the purpose and functioning of which is discussed below.
  • TX/RX CONTROLLER 34 defines transmission and receiving times by selectively activating antenna driver 14 by signals on line 36. Controller 34 also controls operating times of harmonic suppressor 32 signals generated on lines 38 and 40.
  • Voltage limiting diodes 42 and 44 are connected in oppositely polarized manner across lines 18 and 20 as in the prior art system for the aforementioned receiver protection.
  • Driver 14 may be implemented by circuitry shown in the incorporated '696 patent.
  • Controller 34 may be implemented by the circuitry controlling switch 16 of Fig. 1 of the '696 patent and otherwise by additional circuit means for generating respective positive and negative voltages on lines 38 and 40 during the period of closure of switch 16 of the '696 patent.
  • harmonic suppressor 32 is a balanced electric circuit, counterpart to the balanced receiver antenna of Fig. 1.
  • the receiving antenna output is applied across the first and second series circuits by lines 28 and 30.
  • the voltages on lines 38 and 40 are present only during system transmitting periods, and the lines have no voltages applied thereto during receiving periods.
  • Fig. 2 preferably with MOSFET type IRFD110/N and type 1RFD9120/P, commercially available from International Rectifier.
  • a characteristic of a MOSFET significant to the subject invention is RDS(on), i.e., static drain-to-source "on" resistance, which, for the above-identified MOSFETs, is a maximum of 0.6 ohm. With two thereof in series, the maximum resistance is 1.2 ohms.
  • a typical diode used for receiver voltage limiting is a 1N4003, which, with one ampere (peak) flowing through it, exhibits a resistance of about 0.96 ohm. In order to reduce diode current to ten milliamps peak, the junction voltage must be held below 0.6 volt peak.
  • the protection diodes remain in place for their desired voltage limiting role in receiver and receiver coil protection.
  • the effects of their nonlinear conduction characteristics can be greatly reduced if not eliminated by applicants' adjunct thereto, i.e., a current demanding electronic switch with substantially linear conduction characteristics.
  • harmonic suppressor 32' is for use with a grounded a version of a receiving antenna connected across lines 28 and 30.
  • MOSFET 58 has its gate connected to line 40 and is connected across lines 28 and 30.
  • MOSFET 60 is of polarity opposite that of MOSFET 58, has its gate connected to line 38 and is likewise connected across lines 28 and 30, i.e., in parallel with MOSFET 58.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
EP95111028A 1994-10-06 1995-07-14 Système électronique impulsionnel de surveillance d'article Expired - Lifetime EP0706157B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US319263 1994-10-06
US08/319,263 US5512878A (en) 1994-10-06 1994-10-06 Pulsed electronic article surveillance systems

Publications (2)

Publication Number Publication Date
EP0706157A1 true EP0706157A1 (fr) 1996-04-10
EP0706157B1 EP0706157B1 (fr) 2000-05-31

Family

ID=23241527

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95111028A Expired - Lifetime EP0706157B1 (fr) 1994-10-06 1995-07-14 Système électronique impulsionnel de surveillance d'article

Country Status (6)

Country Link
US (1) US5512878A (fr)
EP (1) EP0706157B1 (fr)
JP (1) JPH08124046A (fr)
BR (1) BR9504294A (fr)
CA (1) CA2151671C (fr)
DE (1) DE69517275T2 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2741980B1 (fr) * 1995-12-01 1998-01-23 Pierre Raimbault Procede de mise en phase d'etiquettes electroniques station d'interrogation et etiquette electronique pour sa mise en oeuvre
US5942977A (en) * 1997-08-13 1999-08-24 Ludwig Kipp Radio transponder
ITAR20000040A1 (it) * 2000-09-08 2002-03-08 Alessandro Manneschi Trasduttore lettore di transponder per il controllo dei passaggi
US6750768B2 (en) * 2002-04-15 2004-06-15 Wg Security Products, Inc. EAS system employing pseudorandom coding system and method
US6753821B2 (en) * 2002-04-22 2004-06-22 Wg Security Products, Inc. Method and arrangement of antenna system of EAS
US7075304B2 (en) * 2003-10-01 2006-07-11 The Johns Hopkins University Variable damping induction coil for metal detection
US8450997B2 (en) * 2009-04-28 2013-05-28 Brown University Electromagnetic position and orientation sensing system

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5239696A (en) 1991-10-15 1993-08-24 Sensormatic Electronics Corporation Linear power amplifier utilizing current feedback

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8701565A (nl) * 1987-07-03 1989-02-01 Nedap Nv Identificatiesysteem met twee werkingsmodes.
US5121103A (en) * 1988-07-29 1992-06-09 Knogo Corporation Load isolated article surveillance system and antenna assembly
US5103209A (en) * 1989-01-09 1992-04-07 Checkpoint Systems, Inc. Electronic article surveillance system with improved differentiation
GB9004431D0 (en) * 1990-02-28 1990-04-25 Scient Generics Ltd Detection system for security systems
US5300922A (en) * 1990-05-29 1994-04-05 Sensormatic Electronics Corporation Swept frequency electronic article surveillance system having enhanced facility for tag signal detection
US5266926A (en) * 1991-05-31 1993-11-30 Avid Marketing, Inc. Signal transmission and tag power consumption measurement circuit for an inductive reader
US5304983A (en) * 1991-12-04 1994-04-19 Knogo Corporation Multiple pulse responder and detection system and method of making and using same
US5353011A (en) * 1993-01-04 1994-10-04 Checkpoint Systems, Inc. Electronic article security system with digital signal processing and increased detection range
US5373301A (en) * 1993-01-04 1994-12-13 Checkpoint Systems, Inc. Transmit and receive antenna having angled crossover elements

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5239696A (en) 1991-10-15 1993-08-24 Sensormatic Electronics Corporation Linear power amplifier utilizing current feedback

Also Published As

Publication number Publication date
JPH08124046A (ja) 1996-05-17
BR9504294A (pt) 1996-10-01
DE69517275T2 (de) 2000-11-30
DE69517275D1 (de) 2000-07-06
CA2151671C (fr) 2007-02-27
CA2151671A1 (fr) 1996-04-07
US5512878A (en) 1996-04-30
EP0706157B1 (fr) 2000-05-31

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